Answer:
There are two main branches within the Reformed Church family tree in America: Dutch Reformed and German Reformed. Both branches represent churches that separated from the Roman Catholic Church as part of the Protestant Reformation in Europe. The Dutch Reformed branch can be traced back to the Dutch settlers who gathered in New Amsterdam in 1628. The German Reformed branch was started by German immigrants who settled around Philadelphia in the early 1700s. These two branches have much in common, yet have remained distinct throughout their history.

The Dutch Reformed Church maintained ecclesiastical ties to Holland until 1819, when they were incorporated as the Reformed Protestant Dutch Church. In 1867, the name was changed to the Reformed Church in America. The Reformed Church in America has over 300,000 members and is a founding member of the National Council of Churches and the World Council of Churches. According to the church website, the church seeks “to strike a balance between accepting people the way they are and encouraging them to live by Christian standards of fidelity, forgiveness, and growth.”

The Christian Reformed Church, with 268,000 members currently, was formed in 1857 when several congregations in Michigan split from the Dutch Reformed Church over a perceived lack of solid doctrine and biblical practice. Abraham Kuyper was a key leader in building the new denomination, helping them focus on the lordship of Jesus Christ over all of life (Ephesians 1:22). A key distinctive is to “take on the world for Christ—using Christian schools, institutions, and organizations to make God's redemptive and recreating work a reality in the marketplace, city hall, and factory.” Cornelius Plantinga, Reformed theologian and president of Calvin Theological Seminary, writes, “Our accents lie more on the sovereignty of God, on the authority of Scripture, on the need for disciplined holiness in personal Christian life, and finally, on Christianity as a religion of the Kingdom.”

The German Reformed Church was formed in 1725 near Philadelphia and eventually took the name Reformed Church in the US (RCUS). One of the great leaders of this church was Philip Schaff, who was a highly respected writer and editor. His works on church history and the Apostolic Fathers are still widely used today, more than 100 years after his death. In 1934, the RCUS merged with the Evangelical Synod of North America to form the United Church of Christ. A sizable group of churches rejected that merger and formed a reorganized church retaining the name RCUS.

Reformed theology is a body of doctrine that is taught by many different churches, including Presbyterian and some Baptist churches. This body of doctrine reflects the teachings of the Protestant reformers Ulrich Zwingli and John Calvin and is also referred to as Calvinism. The Synod of Dort (1618) was called to answer the teachings of Arminianism and summarized Calvinist doctrine in five points: 1) Total Depravity of Man, 2) Unconditional Election, 3) Limited Atonement, 4) Irresistible Grace, 5) Perseverance of the Saints. These five points are often referred to by the acronym “TULIP.” Reformed theologians have added a great deal of knowledge to the church at large and are generally respected for their solid scholarship.